Cognitive impairments associated with periventricular white matter hyperintensities are mediated by cortical atrophy

Vascular burden and cognition: Mediating roles of neurodegeneration and amyloid PET

It remains unclear to what extent cerebrovascular burden relates to amyloid beta (Aβ) deposition, neurodegeneration, and cognitive dysfunction in mixed disease populations with small vessel disease and Alzheimer's disease (AD) pathology. In 120 subjects, we investigated the association of vascular burden (white matter hyperintensity [WMH] volumes) with cognition. Using mediation analyses, we tested the indirect effects of WMH on cognition via Aβ deposition (¹⁸ F-AV45 positron emission tomography [PET]) and neurodegeneration (cortical thickness or ¹⁸ F fluorodeoxyglucose PET) in AD signature regions. We observed that increased total WMH volume was associated with poorer performance in all tested cognitive domains, with the strongest effects observed for semantic fluency. These relationships were mediated mainly via cortical thinning, particularly of the temporal lobe, and to a lesser extent serially mediated via Aβ and cortical thinning of AD signature regions. WMH volumes differentially impacted cognition depending on lobar location and Aβ status. In summary, our study suggests mainly an amyloid-independent pathway in which vascular burden affects cognitive function via localized neurodegeneration. HIGHLIGHTS: Alzheimer's disease often co-exists with vascular pathology. We studied a unique cohort enriched for high white matter hyperintensities (WMH). High WMH related to cognitive impairment of semantic fluency and executive function. This relationship was mediated via temporo-parietal atrophy rather than metabolism. This relationship was, to lesser extent, serially mediated via amyloid beta and atrophy.

Cognitive impairment in mild traumatic brain injury: a diffusion kurtosis imaging and volumetric study

BACKGROUND

A significant number of patients with mild traumatic brain injury (mTBI) would experience cognitive deficit.

PURPOSE

To investigate the brain structural changes in sub-acute mTBI by diffusion kurtosis imaging (DKI) and volumetric analysis, and to assess the relationship between brain structural changes and cognitive functions.

MATERIAL AND METHODS

A total of 23 patients with sub-acute mTBI and 24 control participants were recruited. All the participants underwent examinations of neuropsychological tests, DKI, and magnetic resonance imaging (MRI)-based morphological scans. Images were investigated using whole brain-based analysis and further regions of interest-based analysis for subcortical nuclei. The neuropsychological tests were compared between the mTBI and the control group. Correlation analysis was performed to examine the relationship between gray matter (GM) volume, DKI parameters, and cognitive functions.

RESULTS

Compared with control participants, mTBI patients performed worse in the domains of verbal memory, attention and executive function (P < 0.05). No regional GM volume differences were observed between the mTBI and control groups (P > 0.05). Using DKI, patients with mTBI showed lower mean kurtosis (MK) in widespread white matter (WM) regions and several subcortical nuclei (P < 0.05), and higher mean diffusivity (MD) in the right pallidum (P < 0.05). Lower MK value of multiple WM regions and several subcortical nuclei correlated with cognitive impairment (P < 0.05).

CONCLUSION

DKI was sensitive in detecting brain microstructural changes in patients with sub-acute mTBI showing lower MK value in widespread WM regions and several subcortical nuclei, which were statistically associated with cognitive deficits.

Sex Differences in Cerebral Small Vessel Disease: A Systematic Review and Meta-Analysis

Background: Cerebral small vessel disease (SVD) is a common cause of stroke, mild cognitive impairment, dementia and physical impairments. Differences in SVD incidence or severity between males and females are unknown. We assessed sex differences in SVD by assessing the male-to-female ratio (M:F) of recruited participants and incidence of SVD, risk factor presence, distribution, and severity of SVD features. Methods: We assessed four recent systematic reviews on SVD and performed a supplementary search of MEDLINE to identify studies reporting M:F ratio in covert, stroke, or cognitive SVD presentations (registered protocol: CRD42020193995). We meta-analyzed differences in sex ratios across time, countries, SVD severity and presentations, age and risk factors for SVD. Results: Amongst 123 relevant studies (n = 36,910 participants) including 53 community-based, 67 hospital-based and three mixed studies published between 1989 and 2020, more males were recruited in hospital-based than in community-based studies [M:F = 1.16 (0.70) vs. M:F = 0.79 (0.35), respectively; p < 0.001]. More males had moderate to severe SVD [M:F = 1.08 (0.81) vs. M:F = 0.82 (0.47) in healthy to mild SVD; p < 0.001], and stroke presentations where M:F was 1.67 (0.53). M:F did not differ for recent (2015-2020) vs. pre-2015 publications, by geographical region, or age. There were insufficient sex-stratified data to explore M:F and risk factors for SVD. Conclusions: Our results highlight differences in male-to-female ratios in SVD severity and amongst those presenting with stroke that have important clinical and translational implications. Future SVD research should report participant demographics, risk factors and outcomes separately for males and females. Systematic Review Registration: [PROSPERO], identifier [CRD42020193995].

Predicting the Emergence of Major Neurocognitive Disorder Within Three Months After a Stroke

Background: Neurocognitive disorder (NCD) is common after stroke, with major NCD appearing in about 10% of survivors of a first-ever stroke. We aimed to classify clinical- and imaging factors related to rapid development of major NCD 3 months after a stroke, so as to examine the optimal composition of factors for predicting rapid development of the disorder. We hypothesized that the prediction would mainly be driven by neurodegenerative as opposed to vascular brain changes. Methods: Stroke survivors from five Norwegian hospitals were included from the "Norwegian COgnitive Impairment After STroke" (Nor-COAST) study. A support vector machine (SVM) classifier was trained to distinguish between patients who developed major NCD 3 months after the stroke and those who did not. Potential predictor factors were based on previous literature and included both vascular and neurodegenerative factors from clinical and structural magnetic resonance imaging findings. Cortical thickness was obtained via FreeSurfer segmentations, and volumes of white matter hyperintensities (WMH) and stroke lesions were semi-automatically gathered using FSL BIANCA and ITK-SNAP, respectively. The predictive value of the classifier was measured, compared between classifier models and cross-validated. Results: Findings from 227 stroke survivors [age = 71.7 (11.3), males = (56.4%), stroke severity NIHSS = 3.8 (4.8)] were included. The best predictive accuracy (AUC = 0.876) was achieved by an SVM classifier with 19 features. The model with the fewest number of features that achieved statistically comparable accuracy (AUC = 0.850) was the 8-feature model. These features ranked by their weighting were; stroke lesion volume, WMH volume, left occipital and temporal cortical thickness, right cingulate cortical thickness, stroke severity (NIHSS), antiplatelet medication intake, and education. Conclusion: The rapid (<3 months) development of major NCD after stroke is possible to predict with an 87.6% accuracy and seems dependent on both neurodegenerative and vascular factors, as well as aspects of the stroke itself. In contrast to previous literature, we also found that vascular changes are more important than neurodegenerative ones. Although possible to predict with relatively high accuracy, our findings indicate that the development of rapid onset post-stroke NCD may be more complex than earlier suggested.

Cognitive Function and White Matter Lesions in Medication-Overuse Headache

Purpose

This study was designed to investigate the cognitive function and the white matter lesions (WMLs) and the relationship between them in medication-overuse headache (MOH) patients.

Methods

Subjects were enrolled and performed Montreal Cognitive Assessment (MoCA, Chinese-Beijing Version), Hamilton Anxiety Rating Scale (HAMA), Hamilton Depression Rating Scale (HAMD-24), and Pittsburgh Sleep Quality Index (PSQI) to evaluate the general cognitive function, anxiety, depression and sleep quality, and they were divided into three groups according to the MoCA scores: healthy controls, MOH with normal cognition group and MOH with cognitive impairment group. All the participants underwent MRI scans and images were obtained for WML evaluation with Fazekas scale.

Results

One hundred thirty-four participants were enrolled into this study, 46 of them for healthy controls, and 88 for MOH patients, 40 of the MOH patients for MOH with cognitive impairment group, and 48 for MOH with normal cognition group. MOH patients had significantly lower MoCA scores, including the scores of visuospatial and executive function, attention, and orientation, while they had significantly greater HAMA scores, HAMD-24 scores, PSQI scores, and deep white matter hyperintensity scores compared to healthy controls. And in MOH patients, the age, disease duration, monthly headache days, and periventricular white matter hyperintensity scores in patients with cognitive impairment were greater than those in patients with normal cognition. Moreover, the MoCA scores were negatively related to age, disease duration, monthly headache days, and Fazekas scale scores, and disease duration and monthly headache days were significant predictors of cognitive impairment in MOH patients.

Conclusion

MOH patients showed cognitive impairment and increased WML burden. And in MOH patients, cognitive function was negatively related to WML burden, and disease duration and monthly headache days were potential predictors of cognitive impairment. Prompt and effective treatment to stop the progression of the disease may alleviate cognitive impairment in MOH patients.

Cognitive impairment in sporadic cerebral small vessel disease: A systematic review and meta-analysis

This paper is a proposal for an update on the characterization of cognitive impairments associated with sporadic cerebral small vessel disease (SVD). We pose a series of questions about the nature of SVD-related cognitive impairments and provide answers based on a comprehensive review and meta-analysis of published data from 69 studies. Although SVD is thought primarily to affect executive function and processing speed, we hypothesize that SVD affects all major domains of cognitive ability. We also identify low levels of education as a potentially modifiable risk factor for SVD-related cognitive impairment. Therefore, we propose the use of comprehensive cognitive assessments and the measurement of educational level both in clinics and research settings, and suggest several recommendations for future research.

Cortical thickness, white matter hyperintensities, and cognition after stroke

BACKGROUND

A thinner cerebral cortex is associated with higher white matter hyperintensity burden and cognitive impairment in community-dwelling and dementia cohorts. It is important to assess these associations in people with ischemic stroke because their cerebrovascular disease profiles are different to these cohorts.

AIMS

We aimed to determine whether cortical thickness was related to white matter hyperintensity burden and cognition after ischemic stroke.

METHODS

We measured cortical thickness using advanced normalization tools' "KellyKapowski" function in 244 patients with ischemic stroke or transient ischemic attack from the Virtual International Stroke Trials Archive. We measured white matter hyperintensity burden via quantitative volumes and Fazekas score. We extracted data on vascular risk factors at baseline and Mini Mental State Examination scores at one year. We assessed associations between imaging and clinical data using correlation and multiple linear regression.

RESULTS

Pairwise correlation showed that higher white matter hyperintensity Fazekas score was associated with a thinner cortex (rho = -0.284, P < 0.0001). White matter hyperintensities were generally distributed adjacent to and above the lateral ventricles. Voxel-wise analyses showed statistically significant negative associations between cortical thickness and white matter hyperintensities across fronto-temporal and inferior parietal cortical regions. Mean cortical thickness was positively related to Mini Mental State Examination in pair-wise correlation (r = 0.167, P = 0.0088) but there was no independent association after adjustment for age and white matter hyperintensities (beta = 0.016, P = 0.7874).

CONCLUSIONS

Cortical thickness was not an independent predictor of cognition after ischemic stroke. Further work is required to understand how white matter hyperintensities are associated with a thinner cortex in temporal regions but less so in more superior regions where white matter hyperintensities are generally found in people with stroke.

Use of Multimodal Magnetic Resonance Imaging Techniques to Explore Cognitive Impairment in Leukoaraiosis

Leukoaraiosis, also referred to as white-matter hyperintensities (WMHs) or age-related white matter changes, is the most frequently seen lesion on brain magnetic resonance images (MRI) in the elderly. LA is a subject of intense research interest, and is correlated with stroke, cognitive impairment or dementia, disturbances, affective disorders, and poor prognoses. Rapid advances in neuroimaging have enabled greater understanding of LA associated with aging-related cognitive decline or dementia. Recently, the techniques of multimodal MRI, such as structural MRI (sMRI), resting-state functional MRI (rs-MRI), cerebrovascular reactivity (CVR), diffusion tensor imaging (DTI), magnetic resonance spectroscopy (MRS), and dynamic contrast-enhanced MRI (DCE-MRI), have been used to explore the underlying mechanism of cognitive impairment in patients with LA. These multimodal MRI techniques may provide further insights into the structural and functional changes of LA with cognitive dysfunction.

Alterations of the cerebral cortex in sporadic small vessel disease: A systematic review of in vivo MRI data

Cerebral small vessel diseases of the brain are a major determinant of cognitive impairment in the elderly. In small vessel diseases, the most easily identifiable lesions, both at post-mortem evaluation and magnetic resonance imaging, lie in subcortical areas. However, recent results obtained post-mortem, particularly in severe cases, have highlighted the burden of cortex lesions such as microinfarcts and diffuse neuronal loss. The recent development of image post-processing methods allows now assessing in vivo multiple aspects of the cerebral cortex. This systematic review aimed to analyze in vivo magnetic resonance imaging studies evaluating cortex alterations at different stages of small vessel diseases. Studies assessing the relationships between small vessel disease magnetic resonance imaging markers obtained at the subcortical level and cortex estimates were reviewed both in community-dwelling elderly and in patients with symptomatic small vessel diseases. Thereafter, studies analyzing cortex estimates in small vessel disease patients compared with healthy subjects were evaluated. The results support that important cortex alterations develop along the course of small vessel diseases independently of concomitant neurodegenerative processes. Easy detection and quantification of cortex changes in small vessel diseases as well as understanding their underlying mechanisms are challenging tasks for better understanding cognitive decline in small vessel diseases.

Peripheral (deep) but not periventricular MRI white matter hyperintensities are increased in clinical vascular dementia compared to Alzheimer's disease

BACKGROUND AND PURPOSE

Vascular dementia (VAD) is a complex diagnosis at times difficult to distinguish from Alzheimer's disease (AD). MRI scans often show white matter hyperintensities (WMH) in both conditions. WMH increase with age, and both VAD and AD are associated with aging, thus presenting an attribution conundrum. In this study, we sought to show whether the amount of WMH in deep white matter (dWMH), versus periventricular white matter (PVH), would aid in the distinction between VAD and AD, independent of age.

METHODS

Blinded semiquantitative ratings of WMH validated by objective quantitation of WMH volume from standardized MRI image acquisitions. PVH and dWMH were rated separately and independently by two different examiners using the Scheltens scale. Receiver operator characteristic (ROC) curves were generated using logistic regression to assess classification of VAD (13 patients) versus AD (129 patients). Clinical diagnoses were made in a specialty memory disorders clinic.

RESULTS

Using PVH rating alone, overall classification (area under the ROC curve, AUC) was 75%, due only to the difference in age between VAD and AD patients in our study and not PVH. In contrast, dWMH rating produced 86% classification accuracy with no independent contribution from age. A global Longstreth rating that combines dWMH and PVH gave an 88% AUC.

CONCLUSIONS

Increased dWMH indicate a higher likelihood of VAD versus AD. Assessment of dWMH on MRI scans using Scheltens and Longstreth scales may aid the clinician in distinguishing the two conditions.

Specific locations within the white matter and cortex are involved in the cognitive impairments associated with periventricular white matter lesions (PWMLs)

The aim of this study was to test the hypothesis that both white matter disruption and the corresponding cortical dysfunction are involved in the cognitive impairments associated with periventricular white matter lesions (PWMLs). Twenty-two PWMLs subjects were divided into cognitively impaired (PWMLs-CI) and normal (PWMLs-CN) groups. Twelve subjects with normal magnetic resonance imaging (MRI) and cognition were recruited as controls. After cognitive evaluation, diffusion tension image (DTI) and resting-state functional MRI (rfMRI) scans, the fractional anisotropy (FA) values of DTI and the fractional amplitude of low-frequency fluctuation (fALFF) values of rfMRI were measured. Finally, correlations between the cognitive scores and MRI values were analyzed in PWMLs subjects. Our results demonstrated that compared with the other groups, the PWMLs-CI group demonstrated significantly decreased scores in Trail-Making Test (TMT), Symbol Digit Modalities Test (SDMT) and Logical Memory Test (LMT). Compared with the PWMLs-CN group, the PWMLs-CI group displayed decreased FA values in the right splenium of the corpus callosum and right posterior cingulum bundle; lower fALFF values in the left frontal middle gyrus, left precentral gyrus, right angular gyrus and right precuneus; and higher fALFF values in the right mid cingulum cortex, right hippocampus amygdala, right cerebellar hemisphere and left vermis. Meanwhile, the cognitive assessment scores were significantly correlated with the FA or fALFF values in some of the above-mentioned white matter or cortical regions. Conclusively, our results indicate that specific regions of WMLs and cortical dysfunction are involved in the cognitive impairments associated with PWMLs.

White Matter Hyperintensities and Mild Cognitive Impairment in Parkinson's Disease

OBJECTIVES

The clinical implications of white matter hyperintensities (WMH) in non-demented Parkinson's disease (PD) have not been thoroughly examined. To address this, we investigated the spatial distribution of WMH and their regional predilection in non-demented patients with mild PD.

METHODS

Cognitive assessments classified the sample into patients with mild cognitive impairment (PD-MCI, n = 25) and patients with no cognitive impairment (PD-NCI, n = 65) based on the recent formal Movement Disorder Task Force diagnostic criteria. The mean age was 65.1 ± 7.7 years, disease duration was 5.3 ± 3.9 years, and Hoehn and Yahr stage was 1.9 ± .4. WMHs were outlined on T2-weighted imaging using a semi-automated technique. The spatial distribution of WMHs were compared between PD-MCI and PD-NCI using voxel-wise lesion probability maps (LPM). General linear models examined the associations between spatially specific WMHs and cognitive domains.

RESULTS

LPM analyses showed significant differences in the spatial distribution of WMH in PD-MCI compared to PD-NCI in widespread regions of the brain (P < .05). PD-MCI demonstrated significantly greater total and periventricular WMHs compared to PD-NCI (P ≤ .02). Spatial distribution of WMHs was also significantly associated with global cognition, performance on the Frontal Assessment Battery and Fruit Fluency (P < .05).

CONCLUSIONS

Voxel-wise LPM analysis revealed differences in the spatial distribution of WMH between PD-MCI and PD-NCI patients, particularly in the periventricular regions. A more widespread extent of WMH might be indicative of cognitive deterioration. Our findings warrant further longitudinal investigation into the importance of WMH spatial distribution as a predictor for conversion from PD to PD with dementia.

Global cortical atrophy (GCA) associates with worse performance in the Montreal Cognitive Assessment (MoCA). A population-based study in community-dwelling elders living in rural Ecuador

BACKGROUND/OBJECTIVE

Increasing numbers of individuals with cognitive impairment are posing economic threads to the developing world. Proper assessment of this condition may be complicated by illiteracy and cross-cultural factors. We conducted a population-based study in elders living in rural Ecuador to evaluate whether the MoCA associated with structural brain damage in less-educated populations.

METHODS

Atahualpa residents aged ≥60 years were identified during a door-to-door survey and invited to undergo MRI for grading GCA. Using a multivariate generalized linear model, we evaluated whether MoCA scores correlates with GCA, after adjusting for demographics, education, cardiovascular health (CVH) status, depression and edentulism.

RESULTS

Out of 311 eligible persons, 241 (78%) were enrolled. Mean age was 69.2±7.5 years, 141 (59%) were women, 199 (83%) had primary school education, 175 (73%) had poor CVH status, 30 (12%) had symptoms of depression and 104 (43%) had edentulism. Average MoCA scores were 18.5±4.7 points. GCA was mild in 108, moderate in 95, and severe in 26 persons. Total and most domain-specific MoCA scores were significantly worse in persons with moderate to severe GCA. In the multivariate model, mean MoCA score was associated with GCA severity (β=2.38, SE=1.07, p=0.027).

CONCLUSIONS

MoCA scores associate with severity of GCA after adjusting for potential confounders, and may be used as reliable estimates of structural brain damage. However, a lower cut-off than that recommended for developed countries, would be better for recognizing cognitive impairment in less educated populations.

Post-stroke cognitive impairment: epidemiology, mechanisms and management

Post-stroke cognitive impairment occurs frequently in the patients with stroke. The prevalence of post-stroke cognitive impairment ranges from 20% to 80%, which varies for the difference between the countries, the races, and the diagnostic criteria. The risk of post-stroke cognitive impairment is related to both the demographic factors like age, education and occupation and vascular factors. The underlying mechanisms of post-stroke cognitive impairment are not known in detail. However, the neuroanatomical lesions caused by the stroke on strategic areas such as the hippocampus and the white matter lesions (WMLs), the cerebral microbleeds (CMBs) due to the small cerebrovascular diseases and the mixed AD with stroke, alone or in combination, contribute to the pathogenesis of post-stroke cognitive impairment. The treatment of post-stroke cognitive impairment may benefit not only from the anti-dementia drugs, but also the manage measures on cerebrovascular diseases. In this review, we will describe the epidemiological features and the mechanisms of post-stroke cognitive impairment, and discuss the promising management strategies for these patients.